Ping? https://gcc.gnu.org/ml/gcc-patches/2016-11/msg03102.html
Don't get confused by the chatter on https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70909. That defect mixes demangler recursion due to malformed symbols with recursion on well-formed ones. This patch fixes the well-formed lambda subset of that recursion problem.
nathan On 11/30/2016 02:06 PM, Nathan Sidwell wrote:
This patch fixes a problem in libiberty's symbol demangler. With a templated forwarding function such as std::forward, we can end up emitting mangled function names that encode lambda information. Lambdas with auto argument types have a synthesized templated operator(), and g++ uses that when mangling the lambda. Unfortunately g++ doesn't notice the template parameters there mean 'auto' and emits regular template parameter references. (This is a bug, see below.) But, as the forwarding function itself is a template, and the lambda is part of a template parameter substitution, we can end up with the demangler recursing unboundedly. In other cases we can fail to demangle (returning null), or demangle to an unexpected type (substituting the current template parameter type into the place of the 'auto'). This patch fixes the demangler by noting when it's printing the argument types of a lambda. In that case whenever we encounter a template parameter reference we emit 'auto', and also inhibit some &/&& smushing that needs checking. AFAICT, once inside a lambda argument list we cannot encounter template parameter references that actually refer to an enclosing template argument list. That means we don't have the problem of disabling this additional check within the argument list printing. I don't think we can meet a nested lambda type either, but the ++...-- idiom seemed safer to me. We cannot do this substitution when parsing the mangled name, because g++ applies the usual squangling back references as-if there really was a template parameter reference. Later squangling references to the type containing the lambda argument may or may not require the reference to be to an enclosing template argument, or be auto, depending on the context of the squangle reference. I've also included a c++ testcase to check the mangling of the lambdas that cause this. While this is a g++ bug, it's an ABI-affecting one, and we shouldn't change the behaviour unintentionally. I've not investigated why the mangler's failing to check is_auto, and will look at that later. I imagine a fix will be -fabi-version dependent. I have filed 78621 to track it. ok? Nick, we originally found this when GDB exploded. If you're ok with it, I'll commit to binutils/gdb when approved for gcc. nathan
-- Nathan Sidwell
